TITLE: GCN CIRCULAR NUMBER: 25562 SUBJECT: LIGO/Virgo S190828j: No Counterparts in DDOTI/OAN Optical Observations DATE: 19/08/30 03:17:58 GMT FROM: Emma Margarita Pereyra Talamantes at IA-UNAM Ensenada Margarita Pereyra (UNAM), Simone Dichiara (GSFC/UMD), Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), Diego Gonzalez (UNAM), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Eleonora Troja (GSFC/UMD), Gabriele Minervini (INAF/IAPS-Rome) and Tanner Wolfram (ASU) report: We observed LIGO/Virgo S190828j event (Minazzoli et al., GCN #25497) with the DDOTI/OAN wide-field imager at the Observatorio Astronomico Nacional on Sierra San Pedro Martir (http://ddoti.astroscu.unam.mx) from 2019-08-28 08:00 to 2019-08-28 11:57 UTC (1.4 to 5.4 hours after the event). We observed approximately 231 square degrees of the sky, with four pointings centered on 22:10:13.126 +45:18:17.26, 21:45:30.680 +39:42:01.13, 21:25:37.437 +32:53:21.57 and 21:07:43.518 +24:13:55.90. We obtained about 21, 16, 18 and 86 minutes total exposure on each pointing, respectively. These regions include about 35% of the 2D probability in the current BAYESTAR map. We calibrated our images against the APASS catalog. Our 10-sigma limiting magnitude are typically between w = 19.2 and w = 19.8. Comparing our 10-sigma detections against the USNO-B1 catalog, we detect no uncataloged sources with significant fading. We thank the staff of the Observatorio Astronomico Nacional in San Pedro Martir. -- *Dr. Margarita Pereyra * *FFTF, Schlumberger Foundation Alumnae* ---------------------------------------------------------------------------------------------------------------- *Catedrático Conacyt* *Instituto de Astronomía de la UNAM,* *Km. 107 Carretera Tijua**na-Ensenada, * *Ensenada Baja California, México. C.P. 22860* Oficina: 405 Skype: margarita-pereyra